The core around which all distributions are built is the Linux kernel. It is the
layer between the user programs and your system hardware. Gentoo provides its
users several possible kernel sources. A full listing with description is
available at the Gentoo Kernel
Guide.

For alpha-based systems we have vanilla-sources (the default 2.4 kernel
source as developed by the linux-kernel developers), development-sources
(vanilla 2.6 kernel source) and alpha-sources (kernel source optimized
for alpha users).

Choose your kernel source and install it using emerge.

In the next example we install the vanilla-sources.
Of course substitute with your choice of sources, this is merely an example:

# emerge vanilla-sources

When you take a look in /usr/src you should see a symlink called
linux pointing to your kernel source:

If this isn't the case (i.e. the symlink points to a different kernel source)
change the symlink before you continue:

# rm /usr/src/linux
# cd /usr/src
# ln -s linux-2.4.24 linux

Now it is time to configure and compile your kernel source. You
can use genkernel for this, which will build a generic kernel as used
by the LiveCD. We explain the "manual" configuration first though, as it is
the best way to optimize your environment.

If you want to manually configure your kernel, continue now with Default: Manual Configuration. If you want to use
genkernel you should read Alternative: Using
genkernel instead.

Default: Manual ConfigurationIntroduction

Manually configuring a kernel is often seen as the most difficult procedure a
Linux user ever has to perform. Nothing is less true -- after configuring a
couple of kernels you don't even remember that it was difficult ;)

However, one thing is true: you must know your system when you start
configuring a kernel manually. Most information can be gathered by viewing the
contents of /proc/pci (or by using lspci if available). You
can also run lsmod to see what kernel modules the LiveCD uses (it might
provide you with a nice hint on what to enable).

Now go to your kernel source directory and execute make menuconfig. This
will fire up an ncurses-based configuration menu.

# cd /usr/src/linux
# make menuconfig

You will be greeted with several configuration sections. We'll first list some
options you must activate (otherwise Gentoo will not function, or not function
properly without additional tweaks).

Activating Required Options

First of all, activate the use of development and experimental code/drivers.
You need this, otherwise some very important code/drivers won't show up:

Now go to File Systems and select support for the filesystems you use.
Don't compile them as modules, otherwise your Gentoo system will not be
able to mount your partitions. Also select Virtual memory, /proc
file system, /dev file system + Automatically mount at boot:

(With a 2.4.x kernel)
File systems --->
[*] Virtual memory file system support (former shm fs)
[*] /proc file system support
[*] /dev file system support (EXPERIMENTAL)
[*] Automatically mount at boot
[ ] /dev/pts file system for Unix98 PTYs
(With a 2.6.x kernel)
File systems --->
Pseudo Filesystems --->
[*] /proc file system support
[*] /dev file system support (OBSOLETE)
[*] Automatically mount at boot
[*] Virtual memory file system support (former shm fs)
(Select one or more of the following options as needed by your system)
<*> Reiserfs support
<*> Ext3 journalling file system support
<*> JFS filesystem support
<*> Second extended fs support
<*> XFS filesystem support

If you are using PPPoE to connect to the Internet or you are using a dial-up
modem, you will need the following options in the kernel:

When the kernel has finished compiling, copy the kernel image to
/boot. In the next example we assume you have configured and
compiled vanilla-sources-2.4.24; recent kernels might create
vmlinux instead of vmlinux.gz.

It is also wise to copy over your kernel configuration file to
/boot, just in case :)

# cp .config /boot/config-2.4.24

Now continue with Installing Separate Kernel
Modules.

Alternative: Using genkernel

If you are reading this section, you have chosen to use our genkernel
script to configure your kernel for you.

Now that your kernel source tree is installed, it's now time to compile your
kernel by using our genkernel script to automatically build a kernel for
you. genkernel works by configuring a kernel nearly identically to the
way our LiveCD kernel is configured. This means that when you use
genkernel to build your kernel, your system will generally detect all
your hardware at boot-time, just like our Live CD does. Because genkernel
doesn't require any manual kernel configuration, it is an ideal solution for
those users who may not be comfortable compiling their own kernels.

Now, let's see how to use genkernel. First, emerge the genkernel ebuild:

# emerge genkernel

Now, compile your kernel sources by running genkernel all.
Be aware though, as genkernel compiles a kernel that supports almost all
hardware, this compilation will take quite a while to finish!

Note that, if your boot partition doesn't use ext2 or ext3 as filesystem you
need to manually configure your kernel using genkernel --menuconfig all
and add support for your filesystem in the kernel (i.e. not as a
module).

Once genkernel completes, a kernel, full set of modules and
initial root disk (initrd) will be created. We will use the kernel
and initrd when configuring a boot loader later in this document. Write
down the names of the kernel and initrd as you will need it when writing
the bootloader configuration file. The initrd will be started immediately after
booting to perform hardware autodetection (just like on the Live CD) before
your "real" system starts up.

# ls /boot/kernel* /boot/initrd*

Now, let's perform one more step to get our system to be more like the Live
CD -- let's emerge coldplug. While the initrd autodetects hardware that
is needed to boot your system, coldplug autodetects everything else.
To emerge and enable coldplug, type the following:

# emerge coldplug
# rc-update add coldplug boot

If you want your system to react to hotplugging events, you would need to
install and setup hotplug as well:

# emerge hotplug
# rc-update add hotplug default

Installing Separate Kernel ModulesInstalling Extra Modules

If appropriate, you should emerge ebuilds for any additional hardware that is
on your system. Here is a list of kernel-related ebuilds that you could emerge:

Ebuild

Purpose

Command

xfree-drm (or x11-drm)
Accelerated graphics for ATI Radeon up to 9200, Rage128, Matrox, Voodoo and
other cards for XFree86. Please check the IUSE_VIDEO_CARDS variable
in the /usr/portage/x11-base/xfree-drm ebuilds to see what you
need to fill in as yourcard. The xfree-drm ebuild has been renamed to
x11-drm after the 2004.3 release.
VIDEO_CARDS="yourcard" emerge xfree-drm

Beware though, some of these ebuilds might deal with big dependencies. To verify
what packages will be installed by emerging an ebuild, use emerge
--pretend. For instance, for the xfree-drm package:

# emerge --pretend xfree-drm

Configuring the Modules

You should list the modules you want automatically loaded in
/etc/modules.autoload.d/kernel-2.4 (or kernel-2.6).
You can add extra options to the modules too if you want.

To view all available modules, run the following find command. Don't
forget to substitute "<kernel version>" with the version of the kernel you
just compiled: